T

4

SEDERHOLMITE, WILKMANITE, KULLERUDITE, M..AKINENITE and TRUSTEDTITE, FIVE NEW MINERALS 1)

BY

Y. VUORELAINEN, A. HUHMA AND A. H.A.KLI

Outokumpu Co., Finland

ABSTRACT

Five new nickel selenide minerals from Kuusamo, NE-Finland are described. The minerals occur in veinlets in albitites associated with uranium mineralisation. Sederholmite, which is identical with the synthetic hexagonal fJ-NiSe phase, has a o = 3.62 - 3.65 A and eo = 5.29 - 5.34 A depending upon composition. Wilkmanite corresponds to the artificial monoclinic Ni3Se4 phase. Its a o = 6.22 A, b o = 3.63 A, CO = 10.52 A and fJ = 90.55°. Kullerudite NiSe 2 is an ortho-rhombic nickelian analogue of ferroselite with a o = 4.89 A, b o = 5.96 A and Co = 3.76 A. M:ikinenite, which is the same as the artificial y-NiSe phase, has a trigonal symmetry with a o = 10.01 A and Co = 3.28 A. Triistedtite is a cubic spinel type Ni3Se4 having a o = 9.94 A. It forms a solid solution series with polydymite. Members of this series with 40-70 mole per cent polydymite component have also been found.

CONTENTS Page INTRODUCTION 114 GEOLOGY OF THE MINERALISATION AREA 115 OCCURRENCE 116 PHYSICAL AND OPTICAL PROPERTIES 117 CHEMICAL COMPOSITION 117 CRYSTALLOGRAPHY 118 NOMENCLATURE 124 ACKNOWLEDGEMENTS 124 REFERENCES 125 1) Received May 6, 1964.

15 10547-64 114 Bulletin de la Commislsion geologique de Finlande N: 0 215.

INTRODUCTION SI n The system nickel-selenium has been studied by various authors. Ac­ SI cording to the literature the following of nickel are known. a-NiSe was obtained by Levi and Baroni (1935) by conducting into a neutral nickel salt solution. The product was amorphous. ~-NiSe, which has a hexagonal structure of the NiAs type (Gr0nvold and Jacobsen, 1956, Hiller and Wegerner, 1960) has been prepared either by b heating appropriate amounts of the elements in evacuated and sealed silica o tubes (Gmnvold and Jacobsen, 1956) or by precipitating it with hydrogen SI selenide in a nickel acetate solution containing acetic acid (Levi and Baroni, a 1935). g y-NiSe has been obtained by Levi and Baroni (1935) by conducting a into a nickel sulphide solution containing sulphuric acid. Hiller and Wegener (1960) have also prepared y-NiSe by heating powdered G nickel and selenium at 225-250 Co. The compound is trigonal with a mill­ b erite type structure.

NiSe 2 has been prepared by de Jong and Willems (1928) by heating a IS mixture of NiSe and selenium at 230 Co for 48 hours. It has also been synthe­ b tised by e.g. Gr0nvold and Jacobsen (1956), Hiller and Wegerner (1960) and Klemm (1962). The NiSe phase has a pyrite structure. 2 cl Ni3Se2 has been reported by Hiller and Wegener (1960). The phase is o hexagonal with a o = 6.029 A and Co = 7.249 A. T The Ni3Se 4 phase has also been prepared by Hiller and Wegenar (1960). s< A~cording to them it is monoclinic with a o = 12.15 A, b o = 3.633 A, Co = ~ 10.45 A and = 149°22'. Gr0nvold and Jacobsen (1956) have derived the Cl ~-NiSe structure of Ni3Se4 from that of the deformed hexagonal cell and b obtained different unit cell dimensions: a o = 6.196 A, b o = 3.634 A, Co = p ~ 10.464 A and = 90.78°. b Only two nickel selenide minerals have been reported so far. Blockite a

(Ni,Cu)Se 2 was described by Herzenberg and Ahlfelt (1935) from Bolivia. tl In fact the mineral is the same as penroseite which was discovered in the h same locality and studied by Gordon (1925). Blockite is structurally similar to the artificial NiSe 2 • Robinson and Brooker (1952) reported a new nickel-bearing selenide, tyrrelite (Cu, Co, Ni)3Se4 from Beaverlodge Lake, Saskatchewan. They suggested that the mineral is structurally similar to pentlandite but Ma­ o chatschki (1952) has pointed out that the powder pattern oftyrrelite resem­ w bles_those of the spineI and linnaeite groups of minerals. A In conl).ections with the prospecting work carried out by the Outokumpu V Co in Kuusamo, in NE Finland during 1961-1963 quite a few new nickel w 1 Suomen Geologinen Seura. N: 0 36. Geologiska SaJlskapet i Finland. 115

selenide minerals were encountered. In this paper five of them i.e. p-NiSe, monoclinic Ni Se , y-NiSe, ortho-rhombic NiSe and cubic Ni Se are de­ Ac- a 4 2 a 4 scribed. illlum hous. GEOLOGY OF THE SELENIUM MINERALISATION AREA. i and In Kuusamo in NE Finland the Se-mineralisation occurs in albite dia­ er by bases which form sills in a schist formation. The schist formation is composed silica of quartzites, dolomites, marls, mica schists and black schists. Also green­ rogen schists are encountered. Quartzites are either clastic ortho-quartzites or lroni, albite-bearing arkose quarzites grading into dolomites. The marls are fine­ grained, predominantly grey, dolomite-bearing sediments which contain, cting apart from dolomite, quartz, micas and albite as major minerals. acid. Ripple marks, fossil mud cracks and clastic dikes are found in sediments. dered Graded bedding which permits the determination of the sedimentation mill- bottom is observed in mica schists and phyllites. In some localities phyllites contain carbon-bearing »bags» with calcite-rich cores. The size of the »bags» mg a is variable but the biggest attain a diametre of about 30 cm. They are nthe­ believed to be of fossil origin. . ) and The green-schists, which may be, at least partly, of volcanic origin are chlorite-albite-epidote rocks often showing a distinct bedding. The bedding Lse IS of the schist formation dips subvertically. Folds as well as faults are common. The formation has locally tectonised intensively giving rise to transverse 960). schistosity. Co = Albite diabase is a hornblende-albite rock of variable grain size. Espe­ i the cially in strongly tectonised places it changes into more fine-grained biotite­ " and bearing rock which contains only a small amount of hornblende or is com­ Co = pletely free from it. Pink albitite is associated with these biotite-albite dia­ bases forming dikes or irregular bodies in the latter. Albitites occur prefer­ ckite ably at the ends or at the flexure points of the albite diabase sills, or near by livia. the country rock contacts i.e. generally in places where tectonisation has 1. the been strongest. milar Small amounts of sulphide, selenide and telluride minerals have been found in albitites, among them some hitherto unknown in geological litera­ nide, ture. These minerals are intimately associated with low-grade uranium min­ They eralisation and especially nickel selenides seem closely to follow uranium. Ma- Outside the uranium mineralisation the nickel content diminishes rapidly, :sem- whereas the amount of cobalt relative to that of nickel increases considerably. A similar correlation has been reported from Shinkolobwe by Derriks and lmpu Vaes (1955). In the wall rock cobalt is incorporated in the lattice of pyrite ickel which can contain up to 3 per cent cobalt. 116 Bulletin de la Commislsion geologique de Finlande N: 0 215. .1 ( The uranium mineralisation, which is confined to albitites, is not homo­ is co geneous but the uranium minerals occur as isolated spots and veinlets. The in th most important mineral is uranite, but brannerite, davidite, kasolite and 'I uranoanatase have also been identified as well as some alteration products afOrE of primary uranium minerals. crys1

II), I const toge1 OCCURRENCE NiTE have Among the new nickel selenides p-NiSe and monoclinic NiaSe4 form a natural and interesting pair. The artificial counterparts of these minerals idior have been prepared and reported by e.g. Levi and Baroni (1935), Gr0nvold and Jacobsen (1956) and Hiller and Wegener (1960). Since p-NiSe changes

into monoclinic NiaSe4 by decreasing nickel content, both minerals occur associated most intimately with each other. They are found almost exclu­ '1 sively in blockite clusters of a few millimetres in diametre, which seem to sitio: favour calcite veinlets in the uranium-bearing parts of albitite dikes. fJ-NiSe is di and monoclinic Ni Se brecciate blockite forming micro-veinlets and flame­ 3 4 greeJ like segregations in it as is seen in Fig. 1, Plate 1. p-NiSe has also been detected yellc as independent grains in clausthalite. Monoclinic NiaSe4 seems to occur either clini, as a primary or secondary mineral. The latter is an alteration product of yellc P-NiSe. The secondary monoclinic NiaSe4 often gives a diffuse powder pattern Botl with the consequence that only the strongest reflections are visible. Mono­ '1 clinic Ni Se is frequently followed by native secondary selenium and some­ a 4 exce times -also by ferroselite. Selenian vaesite and selenian cattierite also belong and to the mineral paragenesis but they are younger than blockite, fJ-NiSe and minE monoclinic NiaSe4 , for they form veinlets cutting the latter. (Sec Fig. 1, I Plate I). is stJ The ortho-rhombic NiSe seems to occur almost exclusively as an altera­ 2 pale tion product of monoclinic NiaSe4 • The mineral grains often contain relics cind of the latter as indicated by Fig. 2, PlateI, but in some cases the primary ( mineral has completely disappeared. The formation of the ortho- rhombic is hi NiSe has taken place soon after the crystallisation of fJ-NiSe and monoclinic 2 hloc: Ni Se but before the appearance of selenian sulphides, for they are seen to 3 4 take cut ortho-rhombic NiSe • In spite of the fact that ortho-rhombic NiSe is a 2 2 NiaS nickelian analogue of ferroselite it has never been observed in association with the latter. Ferroselite seems to be primary. It is distinctly yellow in colour and contains about 5 per cent nickel. y-NiSe was first found combined with clausthalite (see Fig. 3, Plate I) in strin~rs at the ends ofthe veins filled with carbonate, clausthalite,NiTeSe ] (a new minera;l to be described in a forthcoming paper), selenian melonite, qUal hematite and spinel type selenian sulphides. Itgreatly resembles millerite but had Snomen Geologinen Seura. N: 0 36. Geolog,iska Sallskape't i Finl,and. 117

homo­ is considerably softer. Later y-NiSe was also found as submicroscopic grains ,s. The in the cracks of selenian melonite associated with clausthalite. te and The spinel type Ni3 Se4 also belongs to the mineral paragenesis of the oducts aforementioned calcite- and uranium-bearing veinlets. It occurs as.. euhedral crystals in clausthalite in association with blockite and tJ-NiSe (Fig, 4, Plate

II), Cubic Ni3Sc4 seems to form a solid solution with polydymite with the

consequence that Ni3 (Se,S)4 minerals have also been detected. They occupy, together with clausthalite, the very ends of the stringers filled by carbonate, NiTeSe, hematite and Ni-, Co- and Se-bearing pyrite (Fig. 5, Plate II). They orm a have also been found in NiTeSe where they are commonly enveloped by inerals idiomorphic apatite crystals. 2myoId !langes occur PHYSICAL AND OPTICAL PROPERTIES excIu- The optical properties of tJ-NiSe vary somewhat depending upon compo­ Jem to sition. In oil the stoichiometric variant is orange yellow in colour. Pleochroism I1-NiSe ~ is distinct with different hues of yellow. Anisotropism is strong: pinkish ­ flame- greenish. The nickel-deficient type is yellow in colour. Its pleochroism is weak: tected yellow - greyish yellow and anisotropism distinct: pink - greenish. Mono­ either clinic Ni3 Se4 is pale greyish yellow in colour. Pleochroism is distinct: pale uct of , yellow - greyish yellow and anisotropism strong: pink - yellowish green. attern I Both minerals take an easy polish and have a high reflectivity. Mono- I The colour of the ortho-rhombic NiSe is very similar to that of blockite some- I 2 \ except that it is slightly paler. Pleochroism in oil is distinct: grey - pale grey belong and anisotropism very strong: yellowish grey - grey to almost black. The ~e and mineral seldom polishes well and is rather soft. 11g.Cl' 1, r In oil y-NiSe is pure yellow in colour but in air orange yellow. Pleochroism I is strong: pure yellow - greenish yellow and anisotropism extremely strong: 'LItera- pale green - pale orange yellow. In air anisotropism is different: glowing relics l I cinder red - blue green or green. The mineral is almost as soft as clausthalite. 'Imary \ r Cubic Ni3Se4 is yellow in colour and completely isotropic. Its reflectivity ombic is higher than that of tJ-NiSe and blockite and it is only slightly softer than oclinic I blockite. The Ni (Se,S)4 variant is different in colour. It is olive grey and ,een to ( 3 takes an easy polish. Reflectivity is slightly less than that of sulphur-free e 2 IS a Ni3Se4. The mineral is considerably softer than selenian linnaeite. liation low in CHEMICAL COMPOSITION late I) ETeSe Due to their rarity it was impossible to separate the selenide minerals in lonite, quantities sufficient for ordinary wet chemical analyses and their composition [te but had to be determined by X-ray fluorescence methods using chemically ana- 118 Bulletin de la Commislsion geologique de Finlande N: 0 215. l ( lysed nickel selenides as standards. The analyses were carried out by a ( Philips's universal vacuum spectrograph provided with a tungsten tube. The

composition of ,B-NiSe was found to vary from Ni 1 ' 05Se to Nio' 85 Se i.e. from the stoichiometric NiSe to the point at which the ,B-NiSe phase changes into

monoclinic Ni3Se 4 - A typical analysis for a nickel deficient ,B-NiSe is as follows: 36.8 % Ni, 1. 9 % Co and 61. 3 % Se. As a rule the mineral contains about 1-2 per cent cobalt, whereas iron and copper are completely lacking or exist only as impurities. According to an X-ray fluorescence analysis, the most nickel-rich mono­

clinic Ni3Se 4 contained 37.6 % Ni and 61.1 % Se, which gives Nio. 83 Se as the composition for that particular mineral sample. Cobalt is, of course, added to nickel in the above formula. The transition point between hexagonal ,B-NiSe and monoclinic Ni3Se4 phases represented by the above specimen agrees excellently with the composition of the transition point reported by Gmnvold and Jacobsen (1956) i.e. Nio. 82Se. The most nickel deficient monoclinic Ni3 Se 4 contained 33.7 % Ni, 1. 0 %

Co and 65.3 % Se which corresponds closely to the formula Ni3 Se 4 • Again, only traces of copper and iron were detected in this mineral.

An X-ray fluorescence analysis showed ortho-rhombic NiSe 2 to contain 23.1 % Ni, 1.4 % Co, 1.91 % Fe, 0.5 % Cu and 73.1 % Se. The chemical formula for the mineral is thus NiSe 2 within limits of analytical errors. The composition of y-NiSe was also determined by the same method and the mineral was found to contain 41.1 % Ni, 1. 0 % Co and 57.9 % Se. Only traces of copper were detected.

An analysed sample ofcubic Ni3Se 4 mineral contained 29.5 %Ni, 6.4 %Co and 64.1 % Se. Traces of copper were also found. Due to the extremely small amount of the material available it was impossible to determine sulphur accurately. Its concentration was in any case very low, if not altogether nil.

According to the length of the a-axes the sulphur-bearing Ni3 (Se,S)4 minerals contain about 40-70 mole percent of polydymite component. As a rule cobalt percentage seems to be lower than that of the sulphur-free Ni3Se 4 · rep; jJ-N but CRYSTALLOGRAPHY ana The unit cell dimensions and powder patterns for the minerals were ob­ of ( tained with a 114.6 mm diametre camera using silicon as an internal standard. p-N of t The lattice parametres of ,B-NiSe and monoclinic Ni3 Se 4 vary somewhat de­ pending on the composition. The values for a nickel-rich ,B-NiSe are: a o = repl 3.65 A and Co = 5.34 A and for a nickel-deficient one: a o = 3.624 A and Co .. 5.2"'88 A, respectively. These values are plotted in Fig. 1. as a function IS S of the composItion together with the values for the artificial compounds app 1 Suomen Geologinen Seura. N: 0 36. Geologiska Sallskapm i Finland. 119

by a e. The 5.38

. froUl 534 ~s into 532 IS as ntains 0" 5JO tcking .~ .~ 528 " ~ 526 mono­ I v 3Se as 524 added :-NiSe 0. 0.10 0.20 0.30 X_ 19rees nvold 3.66

1.0 % o~ ~gain, .~ 3.~ .'0 "- ~ lntain , 'mical \} 3.62

d and o 0.10 Only (3- I'/;'Se h ex09. %Co C ompos/I/OI7 /'1/1-xSe small Fig. 1. The unit cell dimension of hexagonal p-NiSe plotted lphur against the composition. The white circles: values reported ~r nil. by Gronvold and Jacobsen (1956). The black circles: values obtained from the p-NiSe minerals from Kuusamo. 3e,S)4 Asa i 3Se4 · reported by Gmnvold and Jacobsen (1956). The lattice parametres of the p-NiSe minerals are slightly smaller than those for the synthetic compounds but the difference is obviously insignificant and may be entirely due to the analytical errors. On the other hand it may also be c'aused by a small amount e ob­ of cobalt incorporated in the lattice of the mineral. The space group for dard. p-NiSe is P63 /mmc. In Table 1 the X-ray powder data for the p-NiSe mineral ,t de- of the composition Nio. 85Se is given. a o = The indexing of monoclinic Ni3Se4 has been based on the information and reported by Gmnvold and Jacobsen (1956). The powder data for the mineral ction is shown in Table 2. The data represent the composition of Nio. 78Se which unds approaches Ni3Se 4 very closely. The unit cell dimensions for that particular 120 BulLetin de la Commis'sion geologique de Finlande N: 0 215. l

Table 1. X-ray powder data and lattice dimensions for fJ-NiSe mineral from Knusamo, Tabl NE-Finland. The composition of the mineral is Nio. 85Se. Camera diametre 114.59 mm, f and Cn/Ni radiation. Fern hid I dabs. dcalc· h

001 w 5.27 5.29 a o = 3.624 A 101 VVS 2.70 Co = 2.699 5.288 A 1 102 VS 2.015 2.022 Z = 2 110 S 1.806 1.812 V = 60.14 A3 3 10L 103 ms 1.535 1.537 Dca1c. = 7.06 g/cm 112 ms 1.50 1.495 1 202 m 1.348 1.350 I: 004 1.32 1.322 w 2l 203 mw 1.172 1.173 2 211 m 1.155 1.158 212 m 1. 082 1. 082 I: 2 114 m 1. 067 1. 068 [ 1: , 0: 2: ~ 1 l ; H' 310, ." Table 2. X-ray powder data and lattice dimensions for monoclinic Ni Se mineral from ,,! 3 4 rllli Kuusamo, NE-Finland. Camera diametre 114.59 mm, Cn/Ni radiation.

hId into dabs· dcalc·

002 m 5.25 5.26 I £1,0 - 6.22 A sa1ll 011 w 3,42 3.422 b o - 3.63 A 103 W 3.06 3.078 Co = 10.52 A vah: = 90.53° 112 vsI 2.70 2.700 fJ ,JaC( Z = 2 202 2.700 V = 237.5 A3 3 112 m 2.66 2.677 Dca1c. = 6.96 g/cm 013 w 2.52 2.518 Ni3E 211 vw 2.29 2.295 trat 114 2.02 2.021 vsTI trill' 204 2.025 114 s 2.00 2.004 the 020 s 1.815 1.815 1ncr, 310 vsIII 1.800 1. 799 chal 116 ms 1.532 1.53;, 222 ms 1.497 1,4!)5 obvi 404 m 1.343 1.348 Ni3~ 008 W 1.31 1.315 In 226 wE 1.170 1.172 c' 406 1.173 stru 132 wE 1.158 1.156 and 1.154 132 the 406 1.154 512 wB 1.147 1.144 dem 134 wB 1. OSI 1. OSl r 318 wB 1.066 1.069 of n 028 1. 064 600 vwB 1. 037 1. 037 witb

16 Suomen Geologinen SeuTa. N: 0 36. Geologiska Sallskapet i FinlmlC1. 121

I

samo, ) Table 3. X-ray powder data and lattice dimensions for ortho-rhombic NiSe 2 mineral o mIn, I and ferroselite from Kuusamo, NE-Finland. Camera diametre 114.59 mm, Cll/Ni radiation.

Ferroselite FeSe 2 Ortho-rhombic NiSe 2 mineral

hkl I d hkl I I I I I dobs. I deale·

110 vw 3.69 ao = 4.79 A 110 f 3.79 3.799 ao = 4.89 A 011 W 3.12 3.125 101,020 s 2.86 b o = 5.72 A 020 W 2.98 2.H80 b o =5.!l6 A 101 S 2.935 2.937 111 vs 2.565 Co = 3.58 A 111 vs 2.6-1 2.6:H CO = 3.67 A 120 vs 2.47 120 vs 2.5-15 2.5-16 200 w 2.395 Z =2 200 w 2.-1-1 2.-1-19 Z =2 210 vw 2.21 210 W 2.26 2.265 121 w 2.02 V = 98.2 A3 121 mw 2.095 2.0H2 V = 107.0 A3 211 vs 1.88 211 s 1.925 1.928 130 s 1. 79 Deale. = 130 S 1.8-1 1.8E Deale. = 7.22 gjcm3 002 1. 835 6.72 gjcm3 031 ms 1.69 031 w 1. 75 1.747 221 w 1.63 221 mw 1.685 1.682 112 W 1.595 112 m 1.6l8 1.651 131 1.646 {rUIn 310,022 W 1.5-1 310,022 wB 1.57 1.575 320 w 1.-135 1.4:H 240 w 1. 238 240 w 1.275 1. 27 3 . 312 w I 1.162 312 W 1.195 1.195

sample are: aD = 6.22 A, b o = 3.63 A, Co = 10.52 A and fJ = 90.53°. These values are again in good accordance with the values given by Gr0nvold and Jacobsen. As pointed out by Hiller and Wegener (1960) the fJ-NiSe and monoclinic I Ni Se phases form a continuous solid solution series with variable concen­ \ 3 4 tration of the empty Ni-spaces. These empty spaces are statistically dis­ I tributed in the hexagonal solid solution range, for there are no reflections in the powder pattern indicating a change of the lattice symmetry. With the increasing concentration of the empty spaces the hexagonal fJ-NiSe phase

changes into the monoclinic Ni3Se4 phase, in which the defiency of nickel obviously reaches its maximum. The densities for the fJ-NiSe and monoclinic

Ni3Se 4 phases have been calculated under the assumption that the changes in composition are caused by subtraction of nickel atoms from the fJ-NiSe ( structure. The validity of this assumption has been verified e.g. by Gr0nvold \ and Jacobsen (1956) and Hiller and Wegener (1960). Due to the increase of I the empty Ni-spaces in the fJ-NiSe - monoclinic Ni3 Se 4 solid solution the

density tends to decrease from fJ-NiSe towards Ni3Se 4•

The indexing of the ortho-rhombic NiSe 2 has been based on the structure of marcasite. The powder data for the mineral is given in Table 3 together with those for ferroselite. The mineral is ortho-rhombic with aD = 4.89 A,

16 10547-64 122 Bulletin de la Commission geologique de Finlande N: 0 215. l r Table 4. X-ray powder data and lattice dimensions for y-NiSe mineral from Kuusamo, , Tal NE-Finland compared with those for millerite. Camera diametre 114.59 mm, Cu/Ni ( con radiation. Millerite NiS y-NiSe mineral ASTM 12-41

hkl I I dcalc· hkl I dobs' I dcalc· I I I I

110 60 4.81 a o = 9.620 A 110 m 4.99 5.00 ao = 10.01 A 101 40 2.946 101 vw 3.07 3.070 300 100 2.777 Co = 3.149 A 300 vs 2.88 2.890 Co = 3.28 A 021 65 2.513 021 vs 2.63 2.617 220 12 2,406 220 vw 2.49 2.502 Z =9 211 55 2.228 211 vs 2.325 2.319 51 131 95 1.8631 131 vs 1.95 1.940 V = 284.6 A 410 45 1.8178 410 w 1.892 1.892 3 401 40 1.7372 401 mw 1.81 1.809 Dca1c. = 7.22 g(cm 321 18 1.6340 321 mw 1. 71 1. 701 330 35 1. 6037 330 mw 1.665 1.669 I 002 mw 1.64 1.642 012 25 1. 54 70 012 1.612 ( 331 vw 1.48 1.487 71 600 8 1.3884 600 vw 1.445 1.445 (, I 520 4 1.3343 520 1.388 I 73 312 10 1.3008 312 1.355 042 8 1.2560 042 1.308 GB( 440 6 1. 2023 440 1.251 75: l I:tlli\ 161 4 1.1783 161 1.226 502 6 1.1447 502 1.191 l 422 16 1.1133 422 1.159 1 701 701 1.158 91 710 8 1.1033 710 1.148 ( 152 8 1.0846 152 1.129 621 621 1.129 342 • 12 1.0333 342 1. 076 541 6 1. 01 04 541 1.051 612 G 0.9888 612 mw 1. 035 1. 030 y-l' era

b o = 5.\)(\ A and Co = 3.(\7 A. The space group is probably Pnnm. The X-ray for

powder pattern of ortho-rhombic NiSe 2 has great similarity with that of int( ferroselite (Kullerud and Donnay, 1958) and marcasite, even though the unit of cell parametres for the former are somewhat bigger. The density of the ortho­ sho

rhombic NiSe 2 has been calculated based on the assumption that its structure wit is similar to that of ferroselite. The unit cell dimensions for y-NiSe have been reported by Levi and Baroni tyr (1935) and Hiller and Wegener (1960). According to the latter a o = 10.007 A of 1 · and Co = 3.333 A for the compound. The values obtained from the y-NiSe N13 mineral are: a o = 10.01 A and Co = 3.28 A which agree well with the values of Hiller... and Wegener (1960). The powder pattern for y-NiSe is given in call Table 4 together with that for millerite. The mineral is trigonal and its Th( powder pattern' very similar to that of millerite except that the d-values for (19, 1 Suomen Geologinen Seura. N: 0 36. Geolog,iska Siillskapet i Finland. 123

{ .

~lsamo, \ Table 5. X-ray powder data for Ni3Se4 and Nia(Se,S)4 from Kuusamo, NE-Finland Cu/Ni ( compared with those for polydymite. Camera diametre 114.59 mm, Cu/Ni radiation. Polydymite Nia (Se, 8)4 A8TM 8-106 Kuusamo oc hkl I d I I I I d I I d 111 20 5.50 mw 5.60 mw 5.75 1 A 220 40 3.34 aD = mw 3.40 aD = mw 3.52 aD = 9.94 A 311 90 2.85 9.48 A vs 2.90 9.65 A ms 3.00 A 222 -- w 2.79 ms 2.87 Z=8 400 90 2.36 vs 2.41 vs 2.48 422 30 1.941 v 2.00 - - V = 982.1 A3 511,333 90 1.820 s 1.86 m 1.905 lA 440 100 1.674 vs 1.706 vs 1.755 D ca1c. = 531 10 1.600 - - -- 6.62gjcm3 gjcm3 026 10 1.499 -- - - 533 50 1.444 - - - - 540 - - vw 1.50 -- 622 - ~- - - w 1.498 444 60 1.369 vw 1.395 W 1.434 711,551 20 1.330 vw 1.355 - - 642 30 1.269 f 1.29 - - 731,553 80 1.232 vw 1. 255 vw 1.293 800 70 1.185 vw 1.21 -- 660,822 10 1.117 - - -- 751,555 70 1. 095 -- -- - 662 -- -- w 1.149 840 60 1. 055 vw 1. 07 8 w 1.11 842 - - f 1. 055 - - 911,753 5 1.041 -- - - 664 5 1.010 -- - - 931 50 0.994 - - - -

( I y-NiSe are invariably somewhat bigger. The powder pattern shows the min­ ( eral to be isotype with millerite which has a space group R3m. The powder data for cubic NiaSe4 resemble those for tyrrelite and also (-ray for polydymite very closely. For the sake of comparison the d-values and at of intensities of polydymite, of a Nia(Se,S)4 variant with about 63 mole per-cent unit of polydymite component and of NiaSe4 are given in Table 5. The Table rtho­ shows that the length of the a-axis increases from polydymite towards NiaSe4 ature with increasing Se-content reaching a = 9.94 A at NiaSe4. The space group for the cubic NiaSe4 is obviously the same as that for 1Toni tyrrelite, i.e. Fd3m. The mineral can be considered as the nickelian analogue '07 A of bornhardite (Ramdor, 1955) which has only a slightly longer a-axis than NiSe NiaSe4 • ~lues a The density of the cubic NiaSe4 i.e. 6.62 g/cm has been obtained by m in calculation based on the assumption that it is structurally similar to tyrrelite. d its The density for tyrrelite is 6.6 g/cma, as reported by Robinson and Brooker :s for (1952). 124 Bulletin de la Commis'sion geologique de Finlande N: 0 215.

NOMENCLATURE

The facts presented above suggest the existence offive new nickel selenide minerals. The p-NiSe mineral is named in honour of the late Dr. J. J. Seder­ holm, the former Director of the Geological Survey of Finland, in recognition of his unique and fundamental contribution to Pre-Cambrian geology. The name sederholmite should be applied to hexagonal p-NiSe phase from the stoichiometric NiSe composition to the point at which p-NiSe changes into

monoclinic NiaSe4 phase. DEl{ The monoclinic NiaSe4 mineral is named after the late Dr. W. W. Wilkman as an appreciation of his great contribution to geological knowledge about GOl{ Gno Finland, and the name wilkmanite is proposed to be used for a mineral the

composition of which falls within the range of Ni Q • 82Se - Ni Q • 7Se. HEll For the ortho-rhombic NiSe2 mineral the name kullerudite is suggested HIV in honour of Dr. Gunnar Kullerud, Carnegie Institution of Washington, Geophysical Laboratory, in recognition of Dr. Kullerud's valuable contri­ butions to mineralogy. KLE The y-NiSe mineral is named in honour of the late Dr. Eero lVIiikillen, the former President of the Outokumpu Co. as an acknowledgement of his great rw.il Krr ,," merit in geology and mineralogy, as well as of his achivements in the Finnish mining industry.

The name triistedtite is proposed for the spinel type NiaSe 4 mineral in LEV l),'ll, honour ofthe late Dr. O. Triistedt in recognition of his pioneering work in the ;K;: W', development of prospecting methods which in 1910 led to the discover.')~ of the Outokumpu deposit.

Acknowledgement - The authors are indebted to the Outokumpu Company for permission to publish this paper. Professor Th. G. Sahama and Dr. P. Haapala have read the manuscript poinLulg out errors and suggesting improvements. Professor P. Evrard, Professor O. Knop, Dr. N. Sindeewa and Dr. G. Kullerud have given invaluable aid by sending information about nickel selenide compound,.; thus facilitating the work. Mr. J. Kinnunen M. Sc. has provided the chemical analyses needed for standards. To all the aforementioned persons the authors wish to express their sincere gratitude. • I

Suomen Geologinen Seura. N: 0 36. Geologiska Sallskapet Finland. 125

1enide Seder­ nition

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